Runout test

[Lucky6547]

So a lot of posts say full length bushing dies are way to go for straightest ammo.
Some of those same posts say sizing more than .005” down (ie .342 down to .335 neck diameter) will create runout.

Here’s my experience:
308 custom build for ftr
Lapua Palma brass
Using 185 juggernaut and varget with federal match small rifle primers, great accuracy.

So I have a factory full length bushing die, checked to see if the decap pin will fit in the Palma brass before I sized any. It does not.
I also have Wilson neck size arbor dies. Standard decap pin on that doesn’t fit either. Order a Wilson decap for Palma brass.
Find out fired brass is .342” at the neck. Runout minimal on fired brass.
Loaded rounds at .337”.

Decide to do an experiment.
First batch:
Took out decap pin in full length bushing die. Used .337 bushing in that die. Sized brass. Took sized brass and neck sized in Wilson die with .335 bushing and decapped. Runout right around .001” measured on Sinclair runout tool.
Second batch:
.337” bushing in Wilson neck size die, decap. .335” bushing in full length bushing die. Runout around .003”
Third batch:
.335” bushing in the full length bushing die.
Decap in Wilson with no bushing. Runout around .002”

So sizing more than .005” does indeed create more runout than stepping the neck down. But the order I stepped the necks down actually matters, which I found odd.

On a side note, I have a custom 6br for my wife to shoot f-open with a matched Harrell’s full length bushing die and in that rifle I’m only sizing from .269” fired down to .266” loaded and I get virtually no runout. Perhaps I need to get a matched die from whidden for this 308...

Anyone have similar experiences?
Thanks,
Ken

 

[Bc'z]

1st off I'm an admitted neck sizer. After reading posts about removing expander.
So what the hell let's give it a try.
Took mama's 260 brass, Hornady match grade die .288 bushing, removed decaping rod and full length sized them.
What the hell let's try some Varget n go shoot some groups.
Loaded 3 rounds each moving up .3 for 5 loads. Wow really!!! All loads shot under an inch.
Don't have a run out gauge yet or case comparator, but should have them in bout a week

 

[Bart B.]

I think a one piece gelded full length die whose neck in 1 to 2 thousandths under a loaded round's neck diameter is best. Their neck is perfectly centered on the die's shoulder and body all the time. That keeps those of the case perfectly aligned.

Bushings float around inside a small clearance in such dies.

 

[Lucky6547]

By gelded you mean no expander?
So just get a regular forester and have them ream out the neck to my brass? Or have whidden make a non-bushing and take out the expander?

 

[Bart B.]

By gelded you mean no expander?
So just get a regular forester and have them team out the neck to my brass? Or have whidden make a non-bushing and take out the expander?

Yes, like gelding horses. Honed out Forster or other make full length dies are excellent.

 

[Lucky6547]

Ok, thanks

 

[T-shooter]

I've read that too and usually first reduce the necks with a modified Lee collet die to get within .003" of so of the final size, them run them through a Forster full length die. The ball does not change or increase runout since the shaft it's on floats and centers itself. The neck-turned cases are centered by the outside of the neck and are partially in the neck portion as the ball aligns and starts to be pulled through. If you have a bad piece of brass, no amount of resizing will remove all the runout. If you have brass that refuses to straighten, anneal the necks and shoulders. This will usually cure or help the situation.

 

[JFrank]

I've read that too and usually first reduce the necks with a modified Lee collet die to get within .003" of so of the final size, them run them through a Forster full length die. The ball does not change or increase runout since the shaft it's on floats and centers itself. The neck-turned cases are centered by the outside of the neck and are partially in the neck portion as the ball aligns and starts to be pulled through. If you have a bad piece of brass, no amount of resizing will remove all the runout. If you have brass that refuses to straighten, anneal the necks and shoulders. This will usually cure or help the situation.

I would beg to differ slightly as with my experience the expander ball will push and pull the necks of your brass causing inconsistencies and extra unnecessary trimming
and stress on the necks.
YRMV
J

 

[MagnumManiac]

I have gone away from bushing dies, whether a neck only type or FL die.
The reason is simple. Bushing dies induce donuts, I hate donuts and I hate turning necks, I get no JOY from it whatsoever. I have to turn, but hate it with a passion, would prefer to visit the dentist!

If I work out what size neck I have prior to ordering a Forster FL match/benchrest die set, and order the honed neck version for a modest extra fee, then match my expander and run .002-.003” over the neck diameter, I can barely detect ANY runout after sizing my cases.
I lube my necks and find NO CHANGE in head to shoulder length if I remove the expander.

I truly believe a FL DIE with a properly honed/sized neck is hard to beat for concentricity, even with the expander being used.

Cheers.


P.S.
Just as a side note, try testing your loads with and sans any runout, you may be surprised with the results.
I tested rounds with induced runout from .002”, .004”, .006” & .008”, nary a change was seen on target @ 600mtr.
A real eye opener.

 

[shoot4fun]

P.S.
Just as a side note, try testing your loads with and sans any runout, you may be surprised with the results.
I tested rounds with induced runout from .002”, .004”, .006” & .008”, nary a change was seen on target @ 600mtr.
A real eye opener.

I'm curious; jump or jam bullets for this test?

 

[JFrank]

I have gone away from bushing dies, whether a neck only type or FL die.
The reason is simple. Bushing dies induce donuts, I hate donuts and I hate turning necks, I get no JOY from it whatsoever. I have to turn, but hate it with a passion, would prefer to visit the dentist!

If I work out what size neck I have prior to ordering a Forster FL match/benchrest die set, and order the honed neck version for a modest extra fee, then match my expander and run .002-.003” over the neck diameter, I can barely detect ANY runout after sizing my cases.
I lube my necks and find NO CHANGE in head to shoulder length if I remove the expander.

I truly believe a FL DIE with a properly honed/sized neck is hard to beat for concentricity, even with the expander being used.

Cheers.


P.S.
Just as a side note, try testing your loads with and sans any runout, you may be surprised with the results.
I tested rounds with induced runout from .002”, .004”, .006” & .008”, nary a change was seen on target @ 600mtr.
A real eye opener.

I took off the expander ball ,set my depth to minimum followed my a separate Mandrel step. That helped ,
I'm a Forster guy as well.
Maybe I should call them regarding my 308 I'm trashing my Hornday dies
J

 

[BoydAllen]

First of all, the straightest FL sized cases, with turned necks come from one piece dies that have a neck ID that is correct so that no further work needs to be done, no expander ball or mandre. Secondly, you can expand a neck .001 or so if it is lubed without messing up concentricity. Thirdly, IMO bushing dies do not cause doughnuts. You may have a bushing die, and you may have doughnuts, but one does not cause the other. If your cases are kept from moving forward in the chamber the first time that they are fired, and you only bump shoulders that require it because the case is actually tight in the chamber in that direction, and you only bump .001 based on measurement not feel, you are not going to get doughnuts because of using a bushing die.

 

[T-shooter]

I would beg to differ slightly as with my experience the expander ball will push and pull the necks of your brass causing inconsistencies and extra unnecessary trimming
and stress on the necks.
YRMV
J

I can see where it could in some cases. I had the neck portion of my dies honed so that it only reduces the inside neck diameter .002" - .003" under finished size using neck turned brass. I run the ball as high as possible so the maximum neck surface is still supported in the neck portion of the die by screwing the shaft/ball up until it lightly touches, then back off 1/2 turn. This is with the Forster F/L die bottomed out. The shaft sits on a rubber washer and it can move sideways and align. The factory die would reduce the neck .008" undersize, even more with unturned brass, and then the ball expand it back. That's too much. By pulling too hard or having a ball that doesn't float, it definitely could pull the necks out of alignment and also pull it and the shoulder up, especially with annealed brass.

 

[MagnumManiac]

I'm curious; jump or jam bullets for this test?

No jam, I was using a .020” jump with 130gr Berger VLD Target.
.010” jump with 140gr Berger VLD HUNTER.
I also tested runout in 300WM with 200gr Nosler Accubonds with the same result.
My throats are tight, running .0005”-.001” at most over bullet OD, this is why the runout doesn’t matter much.

People ASSUME runout is bad WITHOUT actually testing the results.
Have you ever checked match ammo for runout?

Cheers.

 

[dmoran]

... Bushings float around inside a small clearance in such dies.

Which they need to (float, for perfect centering), and which the dies are designed to let them do.

 

[Lucky6547]

Yes, like gelding horses. Honed out Forster or other make full length dies are excellent.

Do you think a reamed out forester will induce runout as well if I’m sizing more than .005” as mentioned?

 

[Richard Coody]

Do you think a reamed out forester will induce runout as well if I’m sizing more than .005” as mentioned?

only you can answer that question. your press and your sizing process can also induce runout. the honed forster works well for many.

 

[Dusty Stevens]

Do you think a reamed out forester will induce runout as well if I’m sizing more than .005” as mentioned?

If you turn your necks youll have a better chance not to. If you go to far itll bellmouth it. If you get runout- shoot it out and keep it moving. Let the runout checker gather dust

 

[Bart B.]

Do you think a reamed out forester will induce runout as well if I’m sizing more than .005” as mentioned?

Not likely but that's a lot of sizing. If it works, great.

 

[STS]

I’ll add another variable to the discussion that I discovered a long time ago. One assumption that is being made is that all bushing are straight. That is most definitely not the case. It takes a bit of machining to make the mandrels in the lathe to check concentricity of the bushings but it can be done. I have a small storage box with about 50 bushings that I have acquired over the years. I have another box with 4 or 5 that the hole in the bushing is not concentric with the OD. I found those bushings by diagnosing sized case runout and confirming it on the lathe. They aren’t all created equally.